Wednesday PM winter storms update – what we know, what we don’t

Hello! Just wanted to push out a quick note after my usual perusal of the afternoon forecast models. No big updates to share, but I know some folks are interested in any potential insight — especially as we look ahead to making or canceling weekend plans. (Of course, if you're a "weather weenie" like me, you love to read every nugget of analysis and interpretation you can get your meteorological hands on!)

Before you read further, I recommend you check out my previous forecast from Wednesday morning, so you can get a full picture of how my thought process and our weather situation continues to evolve:

Storm #1: Thursday Night through Friday Midday

The first thing I'll say is that confidence is growing about the forecast for our "little" winter storm, Thursday night into Friday. Snow to start Thursday late evening (9 p.m.), then slow transition to rain from SE to NW overnight. A couple inches of slushy accumulation possible along and west of the NJ Turnpike corridor by the time it wraps up midday Friday (Noon). Biggest impact will be a sloppy Friday morning commute.

I am somewhat concerned about temperatures overall here. My temp forecast has been consistently a few degrees too warm all week long. Will that bias continue through our impending double-dose of wintry weather? If so, would that make for a snowier scene in the Garden State? Maybe. (The weather we get is obviously very sensitive to the exact temperature at a given time.)

Storm #2: Saturday Evening through Sunday

This weekend's winter storm is definitely the larger, stronger, more complicated storm of the pair. Actually, I think I'm going to call it a snow/ice/rain storm going forward to better capture to wintry mix that's coming.

Still nowhere near certain on this forecast, as temperatures look to ride either side of the magical freezing mark for the duration. But here's a rundown of possible scenarios, based on where the major forecast models stand:

GFS model forecast for Saturday night, as a powerful snow/ice/rain storm ramps up over New Jersey. (College of DuPage Meteorology)

--The GFS shows this storm's center of low pressure even farther north than before, right over New Jersey Sunday morning. If you don't want a lot of snow, this should be your favorite solution. Raw model output shows 0" South and 6" North. But those numbers are muddled by wintry mix — remember, this storm is probably going to progress from snow to rain to snow. More importantly, the threat for significant icing and/or a flash freeze threat remains very concerning.

--The Euro is colder and snowier, generally in very good agreement with the general impacts map I published this morning. Southern half of NJ: Heavy rain, some ice, some snow (near 0" accumulation). Northern half of NJ: Heavy snow (~12" maybe far north), heavy ice, some rain. Timeline has slid a bit later again, with the final snow burst possibly lingering into early Monday morning. I have to admit, the sleet/freezing rain potential with this solution for Sunday morning is kind of scary. I hate ice storms - truly nasty business.

--The NAM, a shorter-range mesoscale model, is starting to show the weekend storm, although the model can be unreliable looking so far out. It is a more southerly track, keeping New Jersey on the colder side of the storm longer. More cold air, more snow, more ice, more impactful.

--The Canadian is similar to the Euro, tracking the storm's center south of New Jersey. Again, cold side of the storm equals more snow, less rain.

--The GFS Ensemble is probably the coldest solution of the bunch, promoting an even deeper swath of 6+ inch snow through northern and maybe central NJ. I'm not sure that's entirely realistic, but worth keeping in mind as a "snowiest-case scenario".

--The Euro Ensemble very close to its operational brother for a change. Showing a 97% chance of 6+ inches around Sussex County, New Jersey. A 28% chance of 12+ inches.

Piecing Together the Weekend Forecast

Each of the models tells a story. Each story is still very different. That's not incredibly surprising with over 72 hours to go until onset. Especially with a separate precursor storm to consider as well.

Is 12 inches of snow a lock for North Jersey? Not a certainty, but a possibility.

How about 6 inches? There's growing evidence to support at least that much accumulation at the tippity-top of the state. But the changeover to rain/freezing rain/sleet may have a big impact on those totals.

Is 12 inches of snow going to fall in southern and coastal New Jersey? No way.

How about 6 inches? Still nope, unless the storm makes a big directional shift.

Where will the line be between "mostly snow/ice" and "mostly rain"? I still don't have a confident answer here. See Wednesday morning's forecast map (above) for an educated guess, subject to shift in either direction.

Flash freeze still a concern? Absolutely. Temperatures are expected to nosedive from the lower 50s Sunday morning to the teens (or colder) Sunday night. Dropping so cold so fast means the 2 inches of rain that fell during the day may freeze into a solid sheet of ice. Not fun.

At the very least, the weekend storm's timeline is becoming clearer:
--First flakes arrive Saturday evening with heavy snow overnight.
--Change over to heavy rain as temps rise by Sunday morning.
--Tumbling thermometers through Sunday midday and afternoon cause a return to snow.
--Flash freeze possible later Sunday, as puddles freeze over.
--Precipitation will taper off sometime late Sunday, between late afternoon and Midnight. (Admittedly a very wide window.)

We're getting there. But I'm still not ready to draw a snow map. I'm guess I'll have to piece one together sometime tomorrow. But as I've said all week, we may not have a confident grasp on Storm #2 until Storm #1 wraps up Friday. One storm at a time!

Next weather blog update scheduled for Thursday morning. Hopefully I'll get it published by 7 a.m.

Dan Zarrow is Chief Meteorologist for Townsquare Media New Jersey. Follow him on Facebook or Twitter for the latest forecast and realtime weather updates.